The invention relates to a method for detecting imitation gold, and more particularly, to a pen-like device which is capable of scratching a groove in a surface of the metal article being tested, and then applying a specific acid solution on the test area including the groove to observe whether there is any color change to the metal surface on which the liquid was applied, where such a color change indicates that either the metal article is not gold or the gold content thereof has a karat value which is less than the minimum karat value required for the test.
Unfortunately, counterfeiting has become a way of life, costing governments and persons untold amounts of money. With respect to counterfeit paper currency, U.S. Pat. Nos. 5,063,163, 5,261,954 and 5,393,556 disclose methods of detecting counterfeit paper currency. These tests include applying a test solution having an initial color to any selected area of the paper currency being tested. Accordingly, for genuine paper currency, there will be no change to the color of the test area. However, counterfeit paper currency due to the starch content thereof, and the iodine content in the test solution, will turn the test area to a black coloration to indicate the currency is a counterfeit.
Gold is the most popular metal used for jewelry today. Pure gold is very soft so it is usually mixed with other metals (copper, silver, nickel, zinc) to form an alloy to make it stronger and prevent the easy bending thereof. Actually, all jewelry is made from a gold alloy and not from pure gold. Pure gold is always yellow, where any alloy is less yellow than the pure gold.
In order to ascertain the percentage of gold in an article, each gold alloy is measured by karats. Thus, pure gold is assigned a value of 24K, and one karat in the gold alloy is equal to 1/24 part thereof. Accordingly, 14K has 14 parts of pure gold therein, where the remaining 10 parts thereof are another metal such as copper, silver, zinc, nickel. Depending upon which metals are use in the alloys, a variety of colors can be produced. The higher the karat number, the closer the color is to yellow. Another practice is to plate low karat gold jewelry with a higher karat hold to improve the look thereof.
Many countries have established minimum standards that must be met for articles to be legally called "gold". The laws governing the actual content of gold required in a piece of jewelry, however, vary from country to country. In U.S.A. a "gold" article must be at least 10K. In England and Canada, the "gold" article must be at least 9K. In Italy and France, the "gold" article must be at least 18K. Thus, underkarating is a serious problem around the world.
U.S. Pat. No. 5,218,303 discloses a method of determining the amount of gold or other precious metal in an alloy by driving electrical pulses through an electrolyte wet junction. Additionally, U.S. Pat. No. 4,388,409 discloses a cement test device for detecting imitation gold by using a cast cement carrier impregnated with a complex acid solution, so that an imitation gold material presents a darkened blue color when placed in contact with a surface of the carrier.
Imitation gold has traditionally been detected by its solubility in concentrated nitric acid. When the nitric acid is applied to an area of most imitation gold materials, there is a color change where the area will become dark or black. However, it is found that the nitric acid has no effect on bronze or brass. Accordingly, if a bronze or brass material is made to have a gold appearance, then the nitric acid would not detect the imitation gold article. Usually, hydrochloric acid is added to the nitric acid to form an acqua regia acid solution, well known in the art.
Accordingly, there is presently a need for a method of detecting all types of imitation gold, such as those articles made of bronze or brass, and even those imitation gold articles plated with gold, where the test should be accurate and simple to use, as well as being portable and inexpensive.